This invention relates to a vertical frictionally abrasive roll rice polishing machine, and more particularly, to a vertical frictionally abrasive roll rice polishing machine which makes it possible to polish hulled rice grains by grinding under load condition not feasible hithertofore.
As compared with a horizontal frictionally abrasive roll rice polishing machine, although a vertical grindingly abrasive roll rice polishing machine has the advantage that the generation rate of crushed rice grains is substantially lower than that of crushed rice grains in the horizontal frictionally abrasive roll rice polishing machine, since the vertical grindingly abrasive roll rice polishing machine is a rice polishing machine which polishes hulled rice grains under substantially no pressure, the polishing efficiency in the vertical grindingly abrasive roll rice polishing machine is substantially lower than that in the horizontal frictionally abrasive roll rice polishing machine.
The advantages and drawbacks inherent in the horizontal frictionally and vertical grindingly abrasive roll rice polishing machine will be in detail described hereinbelow. The rice polishing machine illustrated in FIG. 1 is a horizontal frictionally abrasive roll rice polishing machine and in the machine, a rice grain feed screw B and a frictionally abrasive roll C are coaxially mounted on a common horizontal shaft A. The shaft A, screw B and abrasive roll C are surrounded by coaxial horizontal polishing and feed cylinders D, D' with one end of the shaft extending through one end wall of the feed cylinder D'. Hulled rice grains are supplied into the feed cylinder D' at a supply port E formed in the top of the feed cylinder D' adjacent the one end wall through which the one end of the shaft A extends and polished rice grains are discharged out of the feed cylinder D' at a discharge port F formed in the other or opposite end wall of the feed cylinder D'. A resistance cover G is pivoted to the other end wall of the feed cylinder D' right above the discharge port F. Although the horizontal frictionally abrasive rice polishing machine has the advantage that since the rice grains are frictionally polished under a high pressure provided by the resistance cover while being forcibly fed by the feed screw, the rice grains can be rapidly polished, the polishing machine inherently has the drawback that since the rice grains are polished by milling, a substantial amount of crushed rice grains are generated. In addition, in the horizontal frictionally abrasive roll rice polishing machine, since the polishing chamber is also a horizontal structure, some of the rice grains accumulate in a relatively thicker layer by their gravity in a lower portion of the polishing chamber and the rest are distributed in a relatively thinner layer in an upper portion of the polishing chamber resulting in uneven polishing. Nevertheless, due to the fact that a high polishing efficiency is attained and a relatively simple power transmission mechanism can be employed, the horizontal frictionally abrasive roll rice polishing machine is in most cases operated in rice polishing mill for general consumers' rice and the vertical grindingly abrasive roll rice polishing machine is scarcely operated in rice polishing mills for such rice.
FIG. 2 and 3 show two types of vertical grindingly abrasive roll rice polishing machines and in these Figures, reference character I denotes a vertical grindingly abrasive roll mounted on an upper portion of a vertical rotary shaft H for rotation therewith. When hulled rice grains a are supplied into the polishing chamber M at the supply port J above the polishing chamber, the rice grains are polished by the grindingly abrasive roll I (emery stone) rotating about its vertical axis while being stirred up by the roll in the horizontal and the polished rice grains are discharged out of the polishing chamber M via the discharge port K at the lower end of the chamber under centrifugal force produced by the rotating abrasive roll I. In this case, since the discharge port K is located on one side of the vertical axis of the polishing chamber M, the rice grains accumulating at the area shown by the arrow L on the opposite side of the axis of the polishing chamber M can not be easily discharged out of the chamber. Since the abrasive roll I is rotating about its vertical axis at a high speed as high as 2000 fpm in the horizontal, although the rice grains accumulating at the arrow L area may be driven away from the accumulating area by the rotating roll I and discharged out of the polishing chamber via the discharge port K under centrifugal force produced by the roll, when even only a small amount of rice grains a remain in the polishing chamber M or any slight increase occurs in the resisting force provided by the resistance cover G, the polishing chamber M is instantly clogged up with such rice grains resulting in the occurrence of trouble. That is, although the resistance cover G is provided, the cover is a pretended resistance device which offers substantially no resistance to the discharge of the rice grains and thus, the rice polishing machine is an inefficient device from the view point of rice polishing efficiency.
The prior art vertical grindingly abrasive roll rice polishing machine is a machine which can polish hulled rice grains by grinding under a certain load, but the machine is not perfectly satisfactory.
That is, in the rice polishing machine illustrated in FIG. 3, the lower end of the vertical rotary shaft H does not extend beyond the lower end of the abrasive roll I and instead, the upper end of the shaft H extends beyond the upper end of the abrasive roll I and a pulley N is mounted on the extended upper end of the shaft H and drivingly connected to an external drive source. The discharge passage K is provided at the bottom of the polishing chamber M right below the abrasive roll I different from the location of the discharge passage in the machine illustrated in FIG. 2. With the arrangement of the rice polishing machine of FIG. 3, the possibility of accumulation of rice grains at the area as shown by the arrow L is eliminated and thus, the resistance cover G can be provided below the discharge passage K to polish rice grains under grinding load. However, in the rice polishing machine of FIG. 3, the possibility of sudden clogging up of the polishing chamber with rice grains is not perfectly eliminated. And the vertical grindingly abrasive roll rice polishing machine of FIG. 3 has the drawback that hulled rice grains a have to be fed from the supply port J to the polishing chamber M through the clearances defined between the spokes on the pulley N. That is, since the pulley N rotates at a substantially high speed, the rice grains can not flow smoothly into the polishing chamber M and thus, an opening is provided in the top wall of the polishing chamber adjacent one side wall of the chamber eccentric to the vertical axis of the polishing chamber as shown by the arrow P. Such location of the supply port P is unsatisfactory because rice grains are fed to the polishing chamber sideways.